Electrolytic diaphragm and method of making same.



U N ITED STATES PATENT OFFICE.

LEO 1i. BAEKELAND, or YONKERS, NEW YORK, ASSIGNOR TO DEVELOP- MENT AND FUNDING COMPANY, OF NEW YORK, N. Y., A CORPORATION OF NEW JERSEY.

Specification of Letters Patent.

Patented May 28, 1907.

Application filed March 10, 1906. Renewed February 16, 1907. Serial No. 357,756-

To all whmn it may concern:

Be it known that I, L O H. BAE-KELAND, a citizen of the United States, residing at Yonkers, in the county of VVGSiJChQStQI' and State of N ew York, have invented certain new and useful Improvements in Electrolytic Diaphragms and Method of Making Same, of which the following is a specification.

The object of this invention is to provide a diaphragm for electrolytic purposes and speciiically for use in the electrolysis of brine.

The diaphragm may be made of any desired porosity, and its porosity may be afterward modified if occasion therefor should arise: it contains no materials which are subject to solution or attack by brine or by the electrolytic products thereof, and is furthermore strong, flexible and durable. these respects it is superior to any diaphragm of which I am aware.

' My improved diaphragm is more particularly intended for use in the electrolysis of brine under such'conditions that a limited quantity of brine is permitted to percolate from the anode com artment to the region of the cathode where t 1e production and separation Of caustic soda occurs, as, for instance, in an electrolytic cell of the type described'iu U. S. Patent 779,383, issued January 3, 1905, to Clinton Paul Townsend. In a cell of this character it is desirable that the diaphragm should possess a substantially uniform porosity in order that the concentration of the caustic may be substantially uniform over the entire area of the cathode. It is furthermore desirable that the diaphragm should be capable of production in large sheets or surfaces, and that it should be of suflicient strength to permit it to be cleaned mechanic ally without injury. All of these requirements are fulfilled by a diaphragm made in accordance with my invention.

A preferred form of diaphragm is made as follows: To the surface of a base consisting of woven asbestos fabric, commonly known as asbestos cloth, I apply a permeable coating, paste or paint, consisting of an cxid of iron such as Venetian red or Indian red, as-

bestos )owder or e uivalent fillin material and a cementing material or binder which preferably consists of ferric or ferrous hy- (lI'OXldu This paint may be prepared by precipitating 400 cc. of ferric chlorid solution having a specific gravity of about 1.4 byan excess of caustic soda, and adding to the re-' sulting alkaline mass and thoroughly incorporating therewith about 500 grams of ferric oxid and 1,200 ams of asbestos powder, together with so oient water to convert the mixture into a rather thick paint. Such bestos cloth and permitted to dry thereon, when the diaphragm is ready for use.

to is desirable as it distinctly aids by its cementing effect in the production of a coherent and durable coating.

I regard ferrous hydroxid asthe equivalent of ferric hydroxid for my purpose inasmuch as it becomes'wholly or partly converted into ferric hydroxid during the drying of the diaphragm. It possesses over ferric hydroxid the advantage of economy since it is readily pre ared by dissolving'scrap iron in commercia muriatic acid and precipitating the resulting ferrous chlorid solution.

I do not limit myself to the specific ingredients or roportions above noted as preferred. 1e asbestos cloth is in itself quite ervious and its interstices are quite irreguer in size and distribution, rendering it entirely unsuited for my purpose. In the formation of my diaphragm it is necessary that these interstices be filled or covered by an adherent and permeable coating which is substantially unaffected under the conditions of use. The use of organic-materials should be avoided.

My diaphragm differs entirely from sized asbestos sheets or paper hereto ore used for such purposes. Such sheets are difficult to handle without injury even when dry, and

coherence; it is impossible'to clean them by mechanical means. The size employed being organic and usually of a starchy character swells when Wet, therefore reducing the permeability of the diaphragm; such size is furthermore subject toattack by the solution and the products of electrolysis.

I claim 1. A diaphragm comprising a pervious base and a ermeable coating or filling dried thereon, su stantially as described.

' The excess of caustic soda above referred mixture is uniformly spread over the aswhen wet are reduced to a pulp having no 2. A diaphragm comprising a base of woven fabric and a permeablecoating or filling dried thereon, substantially as described.

3. A diaphragm comprising a base of asbestos cloth and a permeable coating or filling dried thereon, substantially as described. 4. A diaphragm comprising a pervious base and a permeable coating or filling dried thereon, said coating containing an ox'id of iron and a binder, substantially as described.

5. A dia hragm comprising a base of asbestos clot 1 and a permeable coating or filling dried thereon, said coating containing an oxid of iron and a binder, substantially as described. i

6. A dia hragm comprising a base of asbestos clot 1 and a permeable coating or filling applied thereto, said coating containing an oxid of iron, a filling material'and a binder substantially as described.

Z. A diaphragm comprising a base of as bestos cloth, and a permeable coating or filling applied thereto, said coating containing an oxid of iron, asbestos and a hydroxid of iron, substantially as described.

8. A dia )hragm comprising a base of asbestos clot and a permeable coating or fill: ing a plied thereto, said coating comprising an al aline mixture of ferric oxid, as estos, and ahydroxid of iron, substantially as described. v

9. The method of making a diaphragm which consists in applying to a pervious base a permeable coating or filling, and drying it thereon, substantially as described. Y

In testimony whereof, I allix my si nature in presence of two witnesses.

LEO H. BAEKELAND.

' Witnesses:

'lHoMAs W. Ivnns, JOHN J. STAHL. 

